1. Targeted T cell cytotoxicity resides in the low density fraction of PBL. Activity can be generated in the high density fraction by treatment with antiCD3 antibody and IL-2. 2. Targeted tumoristatic activity has been detected in a long term in vitro tumor growth assay. This activity resides in the T4+ and T8+ subsets of T cells. 3. Human T cells and K cells targeted with anti-T3 and anti-FcR, heterocrosslinked to anti-tumor antibodies eradicate established human ovarian cancer cells in nude mice. 4. Heterocrosslinked antibodies containing an antibody against a soluble antigen linked to an antibody against a cell surface determinant on an antigen presenting cell (APC), greatly enhance the efficiency of antigen presentation. Enhanced presentation has been seen when antigen was targeted to Fc receptors, surface immunoglobulin, MHC class I and MHC class II molecules on the APC. Targeted antigen presentation is antigen specific and I-A restricted.